The State Board of Education narrowly agreed Tuesday to continue a “safety net” that prevents schools’ A-to-F marks from dropping more than a letter grade in a year.

The board voted 4 to 3 to approve Education Commissioner Tony Bennett's recommendation, extending for another year a rule that protects schools from big changes in their grades.

Board member Sally Bradshaw, who voted against the proposal, said it would lead to the number of F-graded elementary and middle schools dropping significantly, from 262 to 108 this year. That would happen, she said, because the “safety net” would give 154 schools C’s or D’s though they earned F’s.

“I don’t understand when it became acceptable to disguise and manipulate the truth simply because the truth is uncomfortable,” said Bradshaw, who served as former Gov. Jeb Bush’s chief of staff.

The school-grading law was a cornerstone of Bush’s education reform efforts during his two terms as governor

If the data she shared proves to be accurate, the number count of F schools this year would be a record, surpassing the previous high of 78 posted in 2005, according to state figures. The Florida Department of Education has not yet confirmed or commented on the numbers Bradshaw cited during the meeting.

Bennett recommended the board continue the “safety net” after meeting with superintendents earlier this month. They argued that the state’s complicated grading formula — revised and added to last year — would lead to lower grades in 2013, even as student performance on state tests improved or held steady.

Bennett said the state’s school accountability system will undergo an overhaul in coming years when Florida moves to new Common Core standards in language arts and math, and new standardized tests in those subjects. Until that change in 2015, Bennett said, he wants to take a “minimalistic” approach to the current grading system to help create a smooth transition to a new one.

Board members who voted for the proposal said they trusted Bennett’s judgment — and also felt the grading system had become too complicated.

“I don’t think the truth is being revealed in the current grading system,” said Chairman Gary Chartrand, who voted for extending the “safety net” along with board members Ada Armas, John Colon and Barbara Feingold.

Last year, as we reported, the rule helped 388 of the 2,513 schools graded, or about 15 percent. That included at least two Orange County elementary schools that would have been F’s but were D’s because of the rule. Statewide, there were 53 F’s last year.

Board members Kathleen Shanahan and John Padget voted against the extension. Bradshaw said she supported the “reprieve” last year to help schools adjust to the new grading rules but could not again. But she said she could not vote that way again.

Schools that should be F’s but get higher grades “desperately need greater resources, immediate intervention, better instruction,” she added, but won’t necessarily get that help if their grades don’t reflect the depth of the problem.

School grades for elementary and middle schools are expected later this month while high school grades are due out months later. School grades are based largely on student scores on state tests but some other factors, such as graduation rates, contribute to high school grades.